jtag: make cmd_queue_scan_field_clone public

This patch makes the cmd_queue_scan_field_clone function public. This
permits targets to insert fields without affecting the submitted
scan_field list. This will be used in an upcoming target implementation
that needs to insert additional padding bits.

Change-Id: I8fbd3b9b4e413432471f4f1444048932c8fa189e
Signed-off-by: Steven Stallion <stallion@squareup.com>
Reviewed-on: http://openocd.zylin.com/4082
Tested-by: jenkins
Reviewed-by: Matthias Welwarsky <matthias@welwarsky.de>

src/jtag/Makefile.am

@@ -1,6 +1,6 @@
 noinst_LTLIBRARIES += %D%/libjtag.la
 
-JTAG_SRCS =
+JTAG_SRCS = %D%/commands.c
 %C%_libjtag_la_LIBADD =
 
 BUILT_SOURCES += %D%/minidriver_imp.h
@@ -13,7 +13,7 @@ JTAG_SRCS += %D%/zy1000/zy1000.c
 JTAG_MINIDRIVER_DIR = %D%/zy1000
 endif
 if MINIDRIVER_DUMMY
-JTAG_SRCS += %D%/minidummy/minidummy.c %D%/commands.c
+JTAG_SRCS += %D%/minidummy/minidummy.c
 JTAG_MINIDRIVER_DIR = %D%/minidummy
 endif
 
@@ -29,7 +29,6 @@ CLEANFILES += %D%/jtag_minidriver.h
 else
 
 MINIDRIVER_IMP_DIR = %D%/drivers
-JTAG_SRCS += %D%/commands.c
 
 if HLADAPTER
 include %D%/hla/Makefile.am